科學儀器學期末專題報告:外腔半導體雷射機構設計

Abstract

中文摘要 本報告主要研究外腔半導體雷射(ECDL)的機構設計，旨在改善二極體雷射輸出線寬過寬與頻率不穩定之缺點。方法上採用利特羅(Littrow)架構，利用繞射光柵的一階繞射光形成外部共振腔，將約1560 nm 的目標波長反射回二極體以加強光回授，並透過雙色分光鏡引導內二倍頻產生的 780 nm 光束注入銣原子蒸氣室。主要結果成功利用 Shapr3D 與 AutoCAD 完成光機構佈局與光線追跡模擬，將雷射線寬壓低至 500 kHz 以下，並使量測到的二倍頻光功率達 27.80 fW，符合飛瓦級偵測器規格，能有效鎖頻至銣原子躍遷頻率。

Abstract This report focuses on the optomechanical design of an external-cavity diode laser (ECDL), aiming to overcome the broad linewidth and frequency instability of conventional diode lasers. A Littrow configuration is adopted, in which the first-order diffraction from a diffraction grating forms an external resonant cavity and reflects the target wavelength of approximately 1560 nm back into the laser diode to enhance optical feedback. A dichroic beamsplitter is then used to direct the 780 nm beam generated through intracavity second-harmonic generation into a rubidium vapor cell. The results demonstrate the successful completion of the optomechanical layout and ray-tracing simulations using Shapr3D and AutoCAD. The laser linewidth was reduced to below 500 kHz, while the measured second-harmonic power reached 27.80 fW, satisfying the specifications of a femtowatt-level photodetector. The proposed system therefore provides an effective approach for frequency locking to the transition frequency of rubidium atoms.